Michael A Fiddy
University of North Carolina at Charlotte, USA
Title: Managing light by scattering from structured materials
Biography
Biography: Michael A Fiddy
Abstract
Depending on material properties, size and shape, one can manage light-matter interactions, scattering phenomena and exploit resonant responses. More complex scattering units or metaatoms provide the opportunity to realize bulk materials with unusual electromagnetic properties. In this talk we investigate the role of local resonances and the effect of some degree of disorder of the meta-atoms on bulk material properties. Coupling between subwavelength elements can result in very large field enhancements and index values not predicted by an effective medium model. Similarly we describe some of the consequences of subwavelength periodicity of these elements and their role in defining bulk material properties. The consequences of disorder and coupling in metamaterial structures sets limits on the material response due to phase decoherence. One can draw parallels with the random phase approximation (RPA) which is routinely invoked in condensed matter physics. We have investigated the propagation of radiation through small numbers of meta-atoms or metamolecules, close to resonant frequencies, to determine how coupling and scattering affects their Q and bandwidth. From a scattering perspective, the coupling of local evanescent fields into propagating waves also contributes to these effective constitutive parameters in a subtle fashion determined by phase coherence. Depending on the materials employed from which the meta-atoms are fabricated, one can observe nonlinear responses. At microwave frequencies and using pulsed illumination, these structures show evidence of an energy exchange between neighboring (non-orthogonal) resonant modes, suggesting their use for tunable parametric applications as well. We discuss how these properties can be realized at optical frequencies.